Hectograph blanket and backing thereof



pril 9, w. H osmms, JR', Erm..

HECTOGRAPH BLANKT AND BAGKING THEREOF Filed April 13, 1939 @gli Patented 29, 1941 HECTOGRAPH BLANK-ET AND BACKING THEREOF i villiam Hoskins, Jr., La. Grange, and Robert C.

Bour, Chicago, Ill., assignors to Ditto, Incorporated, Chicago, Ill., a corporation of West Virginia.

Application April 13, 1939, Serial No. 267,736 4 claims. l(el. 41s1.6

Thev invention relates to an improved hectograph blanket and backing thereof..

Heretofore hectograph blankets adapted to be formed into rolls have been made with backing materials of different types, such as, for example, pyroxlin coated cloth or papers such as rope paper which may or may not have been impregnatedwith glue, glycerin or the like, and which may or may not have been treated with tanning agents.

However, all papers so treated have a tendency to tear or break when exposed to extremely unfavorable climatic conditions. Cloths, while having much higher mechanical resistance, are also much more expensive. An appreciable part of the cost of the cloth backing heretofore used has been due to the cost of lacquering the cloth, a-

step whchis generally done in order to obtainan improved hectograph blanket. Even when such cloth backings have been impregnated with glue or gelatin, substantial amounts of lacquer have been consumed. In an attempt to overcome this defect ,we have impregnated the cloth with inorganic fillers. Such lled fabrics, however, had a tendency to buckle or contract unevenly when exposed to the gelatin or glue'compositions secured-to the backing for obtaining copies by the hectograph process. Forfthis reasonvsuch hectograph blankets in the form of rolls were not entirely satisfactory.

' We have discovered that the tendency of the lled fabrics to buckle or contract unevenly when exposed to the gelatin or glue copy compositions may be substantially reduced or even entirely eliminated by maintaining a substantial amount of water in the fabric.

In accordance with the present invention the y cloth backing for use in the hectograph blanket is impregnated with a lling composition which contains as an essential ingredient a hygroscopic material adapted to preserve the water content grasses, reference being had to the accompanysubstantial amount of hydroscopic material, and

coated on its outer surface with a protective waterproof lacquer 5.

The inorganic filler may suitably be any solid material which is susceptible to a comminution to a particle size sufficiently low to permit effective use in filling compositions. stances may include silicates such as magnesium silicate, silicon dioxide, calcium carbonate, asbestine, powdered aluminum, and the like.

As hygroscopic substances there may suitably be used any substance having high water retentive qualities and low volatility which does not x interfere or objectionably react with the other of the finished cloth suiiiciently to 'prevent buckmaterials employed in themanufacture of the hectograph blanket. Suitable hygroscopic substances include glycerin, sorbitol, sodium lactate, and invert sugar.

The hygroscopic material is used for the purpose of absorbing water so that even with Wide variations of climatic humidity the` cloth will contain a substantial amount of water. By t'hus keeping the cloth backing always in\ a moist condition the uneven expansion and contraction so objectionable in cloth backings which do notcontain hygroscopic substances is may be mentioned by way of illustration, but

with -no intention of implying any limitation: An unbleached cotton cloth having a/xnesh count of x 70 and weighing approximately 3 lbs. per yard is moistened by water and is then passed under tension under a doctor knife.

To the knife a iilling composition is applied con- Such subtinually, such as, for example, one of the following compositions:

Parts by weight China, clay, 350 mesh 7 Glycerin 4 Water to desired viscosity which in most instances preferably will give the composition the character of afairly thick paste.

Parts China clay 7 Bentonite 1l Sorbitol 2 Diethylene glycol 1 Glycerinn.. 1%,

Parts China clay s-- 6 An invert sugar known to the tradev as Nulomoline 2 50% solution sodium lactate 1 Glycerin 2 Having been impregnated with Y any one of these compositions or similar compositions, the cloth is dried by suitable means. These means may include passing over a hoi; plate, festooning,

passing through a warm air current and any one of the other similar methods known to the art. The backing thus prepared is coated on one side with a pyroxlin lacquer composition and on the other side with a bonding composition such as a drying oil or an adhesive composition containing sulfonated oil, such as shown in my Patent 2,098,662. The copy mass, such as, for example, a gelatinous copying mass of the type frequently referred to as a hectograph copying mass, one type of which is described in my Patent 2,098,662, is then secured to the backing by means of the intermediate bonding layer to form a hectograph blanket such as for example is shown in Figs.

1 and 2.

It is to be understood that the above examples simply illustrate embodiments ofthe invention which have given satisfactory results, and are not intended.y to restrict the invention thereto. It is, for example, not necessary to apply *the hygroscopic substance as an ingredient in the filling composition itself. In some instances lt may be preferred to incorporate the hygroscopic sub-I aaadoei substance or water absorbing agent has beenv applied, so long as the finished product contains an inorganic filler and a hygroscopic substance in quantities sufficient to prevent such expansion or contraction of the cloth with changes in atmospheric humidity as would cause buckling or puckering, or waviness in hectograph blankets made from such cloth in the absence of hygroscopic substances.

The amount of hygroscopic substance neces,- sary for this purpose will vary slightly for different types of hygroscopic substance, but in general should be in the range of approximately 20% to 80% by weight on the basis of the ller.

For hygroscopic substances of the nature of glycerin, salts of hydroxy acids and sugars, the

amount of hygroscopic substance should preferl ably be in the range of 50% to 60% by weight of the clay ller.

The amount of inorganic filler preferably should be such as to ll the interstices of the fabric and cover the fibers so that absorption of lacquer will be at a minimum. v

In addition to the inorganic fillers and hygroscopic substances used in the llingcomposition for the cloth backing, there may also be used other ingredients such as, for example, wetting agents which facilitate penetration of the hygroscopic material.`

While there have been shown and described certain embodiments of the invention, it is to be understood that i-t is capable of many modications. Changes, therefore, may bemade without departing from the spirit and scope of i the invention as described in the appended claims, in which it is the intention to claim all novelty inherentl in the invention as broadly as possible, in View of the prior art.,

stance by passing the cloth through a bath containing the hygroscopic material pure or diluted, or by applying it by rollers, or other means used for applyinga liquid to a cloth. The cloth thus wetted and containing the hygroscopic substance is subsequently, or has previously been lled with the-inorganic fillers in a manner known to the art. Thus is it immaterial how the hygroscopic We claim:

1. A hectograph blanket adapted to be formed into a roll, having a brous backing containing a filling composition comprising an inorganic ller and a hygroscopic organic substance which in its dry state is a water soluble solid.

2. A hectograph blanket adapted to be formed into a roll having a cloth backing impregnated' with! a filling composition comprising an inorganic ller and a substantial amount of invert sugar.

3. A hectograph blanket adapted to berorrlee HOSmNS, JR.. ROBERT C. BOUR. 

